org.apache.zookeeper.server.quorum

Class LearnerSnapshotThrottler

java.lang.Object

org.apache.zookeeper.server.quorum.LearnerSnapshotThrottler

public class LearnerSnapshotThrottler
extends Object

Utility class to limit the number of concurrent snapshots from a leader to observers and followers. LearnerHandler objects should call beginSnapshot(boolean) before sending a snapshot and endSnapshot() after finishing, successfully or not.

Constructor Summary

Constructors

Constructor and Description
LearnerSnapshotThrottler(int maxConcurrentSnapshots)
LearnerSnapshotThrottler(int maxConcurrentSnapshots, long timeoutMillis) Constructs a new instance limiting the concurrent number of snapshots to maxConcurrentSnapshots.

Method Summary

Modifier and Type	Method and Description
LearnerSnapshot	beginSnapshot(boolean essential) Indicates that a new snapshot is about to be sent.
void	endSnapshot() Indicates that a snapshot has been completed.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

LearnerSnapshotThrottler

public LearnerSnapshotThrottler(int maxConcurrentSnapshots,
                                long timeoutMillis)

Constructs a new instance limiting the concurrent number of snapshots to maxConcurrentSnapshots.

Parameters:

maxConcurrentSnapshots - maximum concurrent number of snapshots

timeoutMillis - milliseconds to attempt to wait when attempting to begin a snapshot that would otherwise be throttled; a value of zero means no waiting will be attempted

Throws:

IllegalArgumentException - when timeoutMillis is negative or maxConcurrentSnaphots is less than 1

LearnerSnapshotThrottler

public LearnerSnapshotThrottler(int maxConcurrentSnapshots)

Method Detail

beginSnapshot

public LearnerSnapshot beginSnapshot(boolean essential)
                              throws SnapshotThrottleException,
                                     InterruptedException

Indicates that a new snapshot is about to be sent.

Parameters:

essential - if true, do not throw an exception even if throttling limit is reached

Throws:

SnapshotThrottleException - if throttling limit has been exceeded and essential == false, even after waiting for the timeout period, if any

InterruptedException - if thread is interrupted while trying to start a snapshot; cannot happen if timeout is zero

endSnapshot

public void endSnapshot()

Indicates that a snapshot has been completed.